1. Field of the Invention
The present invention relates to boats, and more particularly, to boats with hulls having twin tunnels, and three sponsons.
2. Description of Related Art
Power boats have differing operating characteristics depending on the shape of their hulls. Deep-V boat hulls are known for their ability to cut through waves and go relatively fast over rough seas. Deep-V hulls also create a large storage space below deck. However, deep-V hulled boats have a tendency to roll uncomfortably in swells, particularly when turned parallel to the line of waves. Also, boats with deep-V hulls produce a large wake with a heavy spray, displace a great deal of water at all speeds, have a relatively high aerodynamic and hydrodynamic resistance, and generally have poor fuel economy. In rough waters, particularly at high speeds, deep-V hulled boats tend to lift high with each wave and slam downward into the next wave producing an extremely uncomfortable ride.
One reason for the poor efficiency of deep-V hull boats is their tendency to ride at an angle to the water with the bow up high and the stern low. Thus, the hull presents a large frontal surface area to encounter wind and water resistance. In addition, visibility is reduced as a result of the high bow. Some boat designers have attempted to overcome this characteristic by adding trim tabs and/or lifting strakes to the hull; however, these additions cause an increase in drag and add to the cost and maintenance of the boat while reducing fuel economy.
Catamaran-hulled boats, which have two parallel pontoons joined by a thin deck and an open space between them, offer greater lateral stability than deep-V hulled boats. That is, boats having these hulls have less tendency to roll side to side, especially when resting. Also, catamaran-type hulls tend to create a smaller wake, and operate more efficiently. However, catamaran-type boats offer less storage space and engine space. The performance of a catamaran-hulled boat is affected by how much load is being carried to a greater extent than mono-hulled boats. The amount of water displaced is limited by the volume of the pontoons of a catamaran-type boat making the boat sink further in the water than a mono-hulled boat with the same load. Catamaran-hulled boats tend to ride with the bow higher than the stern but ride more level than a deep-V hulled boat. Catamaran-hulled boats will sometimes flip over backwards at high speeds. This effect is believed to be caused by the lifting force of air on the underside of the thin deck when the bow of the boat is high, a condition which occurs frequently in rough seas. Catamaran hulled boats have an inherent structural weakness in that the pontoons acts as large levers stressing the deck. In rough seas, many decks have been broken by such stresses.
A newer type of hull, the tunnel hull, is normally used on racing boats. This hull has a longitudinal air space or "tunnel" along the center of the boat's bottom. On each side of the tunnel are relatively flat-bottomed hull portions. The high relative velocity between the air in the tunnel and the hull tends to stabilize the boat due to the Bernoulli effect and the air cushions the ride causing a smooth hydrofoil-type ride. However, the tunnel in the center of the hull reduces the storage space below deck. Tunnel-hulled boats tend to remain relatively level at higher speeds which reduces aerodynamic and hydrodynamic resistance and increases visibility. The twin flat hull portions lift the boat to reduce drag at higher speeds. Also, tunnel-hulled boats usually produce less wake and spray. Like a catamaran-hulled boat, a tunnel-hulled boats performance is greatly affected by the weight of the load. Tunnel-hulled boats are well-suited to calm waters but produce a rough ride in choppy water.
Optimal power boat performance requires that the propeller or propellers be what is known as "surface piercing" and be located clear of the boat's stern. Surface piercing propellers operate with the drive shaft near the waterline and the bottom half of the propeller in the water and the top half out of the water. In deep-V hulled boats, standard propeller drives are not surface piercing, however, special articulated drives have been developed for deep-V hulled boats which are surface piercing. In catamaran-hulled boats, standard outboard motors placed between the pontoons will be surface piercing if placed at the proper height, however, standard stern drives built into the pontoons, as in deep-V hulls, require special articulated drives to be surface piercing.
There is a demand in the boating industry for a hull which overcomes the shortcomings of existing designs and provides a smooth ride, good fuel economy, greatly reduced wake and spray, good visibility, high stability, strength, ample space below deck and high acceleration. In addition, there is a demand for a boat hull which enables a standard propeller drive to be surface piercing.